大约有 40,000 项符合查询结果（耗时：0.0356秒） [XML]
How to concatenate strings of a string field in a PostgreSQL 'group by' query?
...at the question asked for, even letting you specify the delimiter string:
SELECT company_id, string_agg(employee, ', ')
FROM mytable
GROUP BY company_id;
Postgres 9.0 also added the ability to specify an ORDER BY clause in any aggregate expression; otherwise, the order is undefined. So you can no...
How to copy text from Emacs to another application on Linux
...Emacs paste and Emacs copy work with system paste, you need to add (setq x-select-enable-clipboard t) to your .emacs. Or try
META-X set-variable RET x-select-enable-clipboard RET t
I think this is pretty standard modern Unix behavior.
It's also important to note (though you say you're using Em...
How to use a class from one C# project with another C# project
...Explorer' tree, expand the P2 project and then right-click the project and select 'Add Reference' from the menu.
On the 'Add Reference' dialog, select the 'Projects' tab and select your P1 project.
If you are using namespaces then you will need to import the namespaces for your P1 types by adding ...
Implement paging (skip / take) functionality with this query
...
In SQL Server 2012 it is very very easy
SELECT col1, col2, ...
FROM ...
WHERE ...
ORDER BY -- this is a MUST there must be ORDER BY statement
-- the paging comes here
OFFSET 10 ROWS -- skip 10 rows
FETCH NEXT 10 ROWS ONLY; -- take 10 rows
If we want...
How to list the tables in a SQLite database file that was opened with ATTACH?
...quently, if you used
ATTACH some_file.db AS my_db;
then you need to do
SELECT name FROM my_db.sqlite_master WHERE type='table';
Note that temporary tables don't show up with .tables either: you have to list sqlite_temp_master for that:
SELECT name FROM sqlite_temp_master WHERE type='table';
...
Oracle取前N条记录方法 Oracle实现SELECT TOP N的方法 - 数据库(内核) - 清...
Oracle取前N条记录方法 Oracle实现SELECT TOP N的方法select * from ( select * from tablexxx order by xxx desc ) where rownum <= Noracle数据库不支持mysql中limit, top功...select * from ( select * from tablexxx order by xxx desc ) where rownum <= N
oracle数据库不支持mysql中li...
MySQL DROP all tables, ignoring foreign keys
... these tweaks:
Limit the generated drops to your database like this:
SELECT concat('DROP TABLE IF EXISTS `', table_name, '`;')
FROM information_schema.tables
WHERE table_schema = 'MyDatabaseName';
Note 1: This does not execute the DROP statements, it just gives you a list of them. You will n...
efficient way to implement paging
...inq (with SQL 2005 / 2008 as database server) your query will be using the Select ROW_NUMBER() Over ... statement, with is somehow direct paging in the SQL engine.
Giving you an example, I have a db table called mtcity and I wrote the following query (work as well with linq to entities):
using (Da...
Can someone explain collection_select to me in clear, simple terms?
I am going through the Rails API docs for collection_select and they are god-awful.
2 Answers
...
Display names of all constraints for a table in Oracle SQL
...CONS_COLUMNS view to see the table columns and corresponding constraints:
SELECT *
FROM user_cons_columns
WHERE table_name = '<your table name>';
FYI, unless you specifically created your table with a lower case name (using double quotes) then the table name will be defaulted to upper ca...